1. Field of the Invention
The present invention relates to a machine for manufacturing folded boxes with sheet material, and is particularly concerned with the drive of a machine which processes corrugated cardboard boxes, i.e. printing, creasing, cutting and folding such boxes.
2. Description of the Prior Art
The machines heretofore known generally process sheets, by printing and cutting the sheets, to manufacture folded and assembled, i.e. glued, boxes.
The first operation to be performed is the printing. Then comes the creasing of the longitudinal folding lines. It should be noted that sheets have already have transverse folding lines thereon. The third operation is the slotting of the front and rear edges of the sheet, in alignment with the folding lines, so that areas, which are to be folded and glued in order to form a box, are created around the sheet. In a fourth operation, holes to ensure ventilation or easy handling of the boxes are cut out of the sheet.
Normally these operations are performed by devices with tools working like mills.
Each printing unit includes a lower printing cylinder operating jointly with an upper pressure cylinder. The creasing elements are constituted by upper and lower tools mounted on four transverse shafts arranged in successive superposed pairs. A slotter unit, also having two pairs of superposed shafts on which the slotting tools are mounted, follows the creasing elements. The slotting tools comprise upper knives mounted around a cylinder and cylindrical lower counterparts facing the upper knives. The slotter can also be provided as well with tools for cutting the lateral edges of the sheets, as with tools for cutting the gluing flaps. The slotter could be provided with two transport bores arranged one above the other and located between the two pairs of superposed shafts to improve sheet transport.
The slotter is followed by a cutting station for special cuts on the blank, such as ventilation holes or handles. This cutting station comprises an upper tool-bearing cylinder acting on a lower angle cylinder made of steel. In certain cases, the anvil cylinder can be made of steel with an elastomer covering. For good transport of the sheets in this unit, conveying elments are mounted on each side of the lower and upper cylinders, as in the slotter.
The upper and lower shafts of the various units are driven by gears ensuring equivalent circumferential speeds for all elements which touch the sheets. There is a device for the angular setting of the slotting and cutting tools, with regard to the position of introduction of the sheets at the entrance of the units. Therefore, the tool-bearing cylinders are set in registration with the sheets to be processed.
The various printing, creasing, slotting and cutting tools are laterally shiftable along their respective shafts, so that they can process boxes of different widths and shapes. These shiftings are performed by moto-reductors driven by a central unit, into which, for example, various values can be registered, according to the size of the boxes to be manufactured. This central unit provides the required orders to the various moto-reductors.
The precreasing, creasing, slotting and cutting units are included in a machine ensuring the feeding, printing, folding and stacking of the different sheets. This type of machine, therefore, enables the manufacturing of a given amount of finished boxes depending on the length of the introduced boxes, and from the circumference of the slotting and cutting tools, for a given speed of the sheet transport. Moreover, as the mechanical driving of the various elements of the machine involves running inaccuracies, the register setting of the various elements is very difficult.
Because of these registration errors, a sheet cannot be processed with great accuracy, and the adjusting of one element with respect to another requires an expensive and complicated structure.